Publications


Modelling Lyman a forest cross-correlations with LyMAS

Monthly Notices of the Royal Astronomical Society 461 (2016) 4353-4373

C Lochhaas, DH Weinberg, S Peirani, Y Dubois, S Colombi, J Blaizot, A Font-Ribera, C Pichon, J Devriendt

© 2016 The Authors.We use the Lya Mass Association Scheme (LyMAS) to predict cross-correlations at z = 2.5 between dark matter haloes and transmitted flux in the Lya forest, and compare to crosscorrelations measured for quasars and damped Lya systems (DLAs) from the Baryon Oscillation Spectroscopic Survey (BOSS) by Font-Ribera et al. We calibrate LyMAS using Horizon-AGN hydrodynamical cosmological simulations of a (100 h -1 Mpc)3 comoving volume. We apply this calibration to a (1 h -1 Gpc)3 simulation realized with 20483 dark matter particles. In the 100 h -1 Mpc box, LyMAS reproduces the halo-flux correlations computed from the full hydrodynamic gas distribution very well. In the 1 h -1 Gpc box, the amplitude of the large-scale cross-correlation tracks the halo bias bh as expected. We provide empirical fitting functions that describe our numerical results. In the transverse separation bins used for the BOSS analyses, LyMAS cross-correlation predictions follow linear theory accurately down to small scales. Fitting the BOSS measurements requires inclusion of random velocity errors; we find best-fitting rms velocity errors of 399 and 252 km s-1 for quasars and DLAs, respectively. We infer bias-weighted mean halo masses of Mh/1012 h-1M⊙ = 2.19+0.16-0.15 and 0.69+0.16-0.14 for the host haloes of quasars and DLAs, with ~0.2 dex systematic uncertainty associated with redshift evolution, intergalactic medium parameters, and selection of data fitting range.


Searches for Sterile Neutrinos with the IceCube Detector.

Physical review letters 117 (2016) 071801-

MG Aartsen, K Abraham, M Ackermann, J Adams, JA Aguilar, M Ahlers, M Ahrens, D Altmann, K Andeen, T Anderson, I Ansseau, G Anton, M Archinger, C Argüelles, TC Arlen, J Auffenberg, S Axani, X Bai, SW Barwick, V Baum, R Bay, JJ Beatty, J Becker Tjus, KH Becker, S BenZvi, P Berghaus, D Berley, E Bernardini, A Bernhard, DZ Besson, G Binder, D Bindig, E Blaufuss, S Blot, DJ Boersma, C Bohm, M Börner, F Bos, D Bose, S Böser, O Botner, J Braun, L Brayeur, HP Bretz, A Burgman, J Casey, M Casier, E Cheung, D Chirkin, A Christov, K Clark, L Classen, S Coenders, GH Collin, JM Conrad, DF Cowen, AH Cruz Silva, J Daughhetee, JC Davis, M Day, JP de André, C De Clercq, E Del Pino Rosendo, H Dembinski, S De Ridder, P Desiati, KD de Vries, G de Wasseige, M de With, T DeYoung, JC Díaz-Vélez, V di Lorenzo, H Dujmovic, JP Dumm, M Dunkman, B Eberhardt, T Ehrhardt, B Eichmann, S Euler, PA Evenson, S Fahey, AR Fazely, J Feintzeig, J Felde, K Filimonov, C Finley, S Flis, CC Fösig, T Fuchs, TK Gaisser, R Gaior, J Gallagher, L Gerhardt, K Ghorbani, W Giang, L Gladstone, T Glüsenkamp, A Goldschmidt, G Golup, JG Gonzalez, D Góra, D Grant, Z Griffith, A Haj Ismail, A Hallgren, F Halzen, E Hansen, K Hanson, D Hebecker, D Heereman, K Helbing, R Hellauer, S Hickford, J Hignight, GC Hill, KD Hoffman, R Hoffmann, K Holzapfel, A Homeier, K Hoshina, F Huang, M Huber, W Huelsnitz, K Hultqvist, S In, A Ishihara, E Jacobi, GS Japaridze, M Jeong, K Jero, BJ Jones, M Jurkovic, A Kappes, T Karg, A Karle, U Katz, M Kauer, A Keivani, JL Kelley, A Kheirandish, M Kim, T Kintscher, J Kiryluk, T Kittler, SR Klein, G Kohnen, R Koirala, H Kolanoski, L Köpke, C Kopper, S Kopper, DJ Koskinen, M Kowalski, K Krings, M Kroll, G Krückl, C Krüger, J Kunnen, S Kunwar, N Kurahashi, T Kuwabara, M Labare, JL Lanfranchi, MJ Larson, D Lennarz, M Lesiak-Bzdak, M Leuermann, L Lu, J Lünemann, J Madsen, G Maggi, KB Mahn, S Mancina, M Mandelartz, R Maruyama, K Mase, R Maunu, F McNally, K Meagher, M Medici, M Meier, A Meli, T Menne, G Merino, T Meures, S Miarecki, E Middell, L Mohrmann, T Montaruli, M Moulai, R Nahnhauer, U Naumann, G Neer, H Niederhausen, SC Nowicki, DR Nygren, A Obertacke Pollmann, A Olivas, A Omairat, A O'Murchadha, T Palczewski, H Pandya, DV Pankova, JA Pepper, C Pérez de Los Heros, C Pfendner, D Pieloth, E Pinat, J Posselt, PB Price, GT Przybylski, M Quinnan, C Raab, M Rameez, K Rawlins, M Relich, E Resconi, W Rhode, M Richman, B Riedel, S Robertson, C Rott, T Ruhe, D Ryckbosch, D Rysewyk, L Sabbatini, J Salvado, SE Sanchez Herrera, A Sandrock, J Sandroos, S Sarkar, K Satalecka, P Schlunder, T Schmidt, S Schöneberg, A Schönwald, D Seckel, S Seunarine, D Soldin, M Song, GM Spiczak, C Spiering, M Stamatikos, T Stanev, A Stasik, A Steuer, T Stezelberger, RG Stokstad, A Stößl, R Ström, NL Strotjohann, GW Sullivan, M Sutherland, H Taavola, I Taboada, J Tatar, S Ter-Antonyan, A Terliuk, G Tešić, S Tilav, PA Toale, MN Tobin, S Toscano, D Tosi, M Tselengidou, A Turcati, E Unger, M Usner, S Vallecorsa, J Vandenbroucke, N van Eijndhoven, S Vanheule, M van Rossem, J van Santen, J Veenkamp, M Voge, M Vraeghe, C Walck, A Wallace, N Wandkowsky, C Weaver, C Wendt, S Westerhoff, BJ Whelan, K Wiebe, L Wille, DR Williams, L Wills, H Wissing, M Wolf, TR Wood, E Woolsey, K Woschnagg, DL Xu, XW Xu, Y Xu, JP Yanez, G Yodh, S Yoshida, M Zoll

The IceCube neutrino telescope at the South Pole has measured the atmospheric muon neutrino spectrum as a function of zenith angle and energy in the approximate 320 GeV to 20 TeV range, to search for the oscillation signatures of light sterile neutrinos. No evidence for anomalous ν_{μ} or ν[over ¯]_{μ} disappearance is observed in either of two independently developed analyses, each using one year of atmospheric neutrino data. New exclusion limits are placed on the parameter space of the 3+1 model, in which muon antineutrinos experience a strong Mikheyev-Smirnov-Wolfenstein-resonant oscillation. The exclusion limits extend to sin^{2}2θ_{24}≤0.02 at Δm^{2}∼0.3  eV^{2} at the 90% confidence level. The allowed region from global analysis of appearance experiments, including LSND and MiniBooNE, is excluded at approximately the 99% confidence level for the global best-fit value of |U_{e4}|^{2}.


Simulated observations of high-redshift galaxies with the HARMONI spectrograph for the European Extremely Large Telescope

Proceedings of SPIE - The International Society for Optical Engineering 9908 (2016)

S Kendrew, S Zieleniewski, RCW Houghton, N Thatte, J Devriendt, M Tecza, F Clarke, K O'Brien, B Häußler

© 2016 SPIE.We show the results of a study into the performance of the E-ELT integral field spectrograph HARMONI for observations of galaxies at 2 < z < 4. Using the instrument simulation pipeline HSIM, we performed mock observations of galaxies in this redshift range using two different methods: (i) passive galaxies modeled with simple analytical spatial profiles and star formation histories; and (ii) a single z = 3 galaxy extracted from a high-resolution cosmological simulation, with a more complex and physically representative morphology and star formation history. We describe the software tools developed to convert the simulation data into a spectral cube containing the spatial and spectral properties of the galaxy's light. From the mock observations we estimate how well the intrinsic properties of the galaxy can be recovered using commonly used analysis tools. The HSIM pipeline also allows us to study observational biases and their likely impact on the data. We discuss the implications of the project for the future science with HARMONI in the critical redshift regime for mass assembly in galaxies.


Thomson scattering measurement of a collimated plasma jet generated by a high-power laser system

Journal of Physics: Conference Series 688 (2016)

T Ishikawa, Y Sakawa, T Morita, Y Yamaura, Y Kuramitsu, T Moritaka, T Sano, R Shimoda, K Tomita, K Uchino, S Matsukiyo, A Mizuta, N Ohnishi, R Crowston, N Woolsey, H Doyle, G Gregori, M Koenig, C Michaut, A Pelka, D Yuan, Y Li, K Zhang, J Zhong, F Wang, H Takabe

© Published under licence by IOP Publishing Ltd.One of the important and interesting problems in astrophysics and plasma physics is collimation of plasma jets. The collimation mechanism, which causes a plasma flow to propagate a long distance, has not been understood in detail. We have been investigating a model experiment to simulate astrophysical plasma jets with an external magnetic field [Nishio et al., EPJ. Web of Conferences 59, 15005 (2013)]. The experiment was performed by using Gekko XII HIPER laser system at Institute of Laser Engineering, Osaka University. We shot CH plane targets (3 mm × 3 mm × 10 μm) and observed rear-side plasma flows. A collimated plasma flow or plasma jet was generated by separating focal spots of laser beams. In this report, we measured plasma jet structure without an external magnetic field with shadowgraphy, and simultaneously measured the local parameters of the plasma jet, i.e., electron density, electron and ion temperatures, charge state, and drift velocity, with collective Thomson scattering.


Search for astrophysical tau neutrinos in three years of IceCube data

PHYSICAL REVIEW D 93 (2016)

MG Aartsen, K Abraham, M Ackermann, J Adams, JA Aguilar, M Ahlers, M Ahrens, D Altmann, T Anderson, I Ansseau, M Archinger, C Arguelles, TC Arlen, J Auffenberg, X Bai, SW Barwick, V Baum, R Bay, JJ Beatty, JB Tjus, K-H Becker, E Beiser, S BenZvi, P Berghaus, D Berley, E Bernardini, A Bernhard, DZ Besson, G Binder, D Bindig, M Bissok, E Blaufuss, J Blumenthal, DJ Boersma, C Bohm, M Boerner, F Bos, D Bose, S Boeser, O Botner, J Braun, L Brayeur, H-P Bretz, N Buzinsky, J Casey, M Casier, E Cheung, D Chirkin, A Christov, K Clark, L Classen, S Coenders, DF Cowen, AHC Silva, J Daughhetee, JC Davis, M Day, JPAM de Andre, C De Clercq, EDP Rosendo, H Dembinski, S De Ridder, P Desiati, KD de Vries, G de Wasseige, M de With, T De Young, JC Diaz-Velez, V di Lorenzo, JP Dumm, M Dunkman, R Eagan, B Eberhardt, T Ehrhardt, B Eichmann, S Euler, PA Evenson, O Fadiran, S Fahey, AR Fazely, A Fedynitch, J Feintzeig, J Felde, K Filimonov, C Finley, T Fischer-Wasels, S Flis, C-C Foesig, T Fuchs, TK Gaisser, R Gaior, J Gallagher, L Gerhardt, K Ghorbani, D Gier, L Gladstone, M Glagla, T Gluesenkamp, A Goldschmidt, G Golup, JG Gonzalez, D Gora, D Grant, JC Groh, A Gross, C Ha, C Haack, AH Ismail, A Hallgren, F Halzen, E Hansen, B Hansmann, K Hanson, D Hebecker, D Heereman, K Helbing, R Hellauer, S Hickford, J Hignight, GC Hill, KD Hoffman, R Hoffmann, K Holzapfel, A Homeier, K Hoshina, F Huang, M Huber, W Huelsnitz, PO Hulth, K Hultqvist, S In, A Ishihara, E Jacobi, GS Japaridze, K Jero, M Jurkovic, A Kappes, T Karg, A Karle, M Kauer, A Keivani, JL Kelley, J Kemp, A Kheirandish, J Kiryluk, J Klaes, SR Klein, G Kohnen, R Koirala, H Kolanoski, R Konietz, L Koepke, C Kopper, S Kopper, DJ Koskinen, M Kowalski, K Krings, G Kroll, M Kroll, J Kunnen, N Kurahashi, T Kuwabara, M Labare, JL Lanfranchi, MJ Larson, M Lesiak-Bzdak, M Leuermann, J Leuner, L Lu, J Luenemann, J Madsen, G Maggi, KBM Mahn, R Maruyama, K Mase, HS Matis, R Maunu, F McNally, K Meagher, M Medici, A Meli, T Menne, G Merino, T Meures, S Miarecki, E Middell, E Middlemas, L Mohrmann, T Montaruli, R Morse, R Nahnhauer, U Naumann, G Neer, H Niederhausen, SC Nowicki, DR Nygren, A Obertacke, A Olivas, A Omairat, A O'Murchadha, T Palczewski, H Pandya, DV Pankova, L Paul, CPDL Heros, C Pfendner, D Pieloth, E Pinat, J Posselt, PB Price, GT Przybylski, J Puetz, M Quinnan, C Raab, L Raedel, M Rameez, K Rawlins, R Reimann, M Relich, E Resconi, W Rhode, M Richman, S Richter, B Riedel, S Robertson, M Rongen, C Rott, T Ruhe, D Ryckbosch, SM Saba, L Sabbatini, H-G Sander, A Sandrock, J Sandroos, S Sarkar, K Schatto, F Scheriau, M Schimp, T Schmidt, M Schmitz, S Schoenen, S Schoeneberg, A Schoenwald, L Schulte, D Seckel, S Seunarine, MWE Smith, D Soldin, M Song, GM Spiczak, C Spiering, M Stahlberg, M Stamatikos, T Stanev, NA Stanisha, A Stasik, T Stezelberger, RG Stokstad, A Stoessl, R Stroem, NL Strotjohann, GW Sullivan, M Sutherland, H Taavola, I Taboada, J Tatar, S Ter-Antonyan, A Terliuk, G Tesic, S Tilav, PA Toale, MN Tobin, S Toscano, D Tosi, M Tselengidou, A Turcati, E Unger, M Usner, S Vallecorsa, J Vandenbroucke, N van Eijndhoven, S Vanheule, J van Santen, J Veenkamp, M Vehring, M Voge, M Vraeghe, C Walck, A Wallace, M Wallraff, N Wandkowsky, C Weaver, C Wendt, S Westerhoff, BJ Whelan, N Whitehorn, K Wiebe, CH Wiebusch, L Wille, DR Williams, H Wissing, M Wolf, TR Wood, K Woschnagg, DL Xu, XW Xu, Y Xu, JP Yanez, G Yodh, S Yoshida, M Zoll, I Collaboration


A review of action estimation methods for galactic dynamics

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 457 (2016) 2107-2121

JL Sanders, J Binney


Measures of three-dimensional anisotropy and intermittency in strong Alfvénic turbulence

Monthly Notices of the Royal Astronomical Society 459 (2016) 2130-2139

A Mallet, AA Schekochihin, BDG Chandran, CHK Chen, TS Horbury, RT Wicks, CC Greenan

© 2016 The Authors.We measure the local anisotropy of numerically simulated strong Alfvénic turbulence with respect to two local, physically relevant directions: along the local mean magnetic field and along the local direction of one of the fluctuating Elsasser fields. We find significant scaling anisotropywith respect to both these directions: the fluctuations are 'ribbon-like' - statistically, they are elongated along both the mean magnetic field and the fluctuating field. The latter form of anisotropy is due to scale-dependent alignment of the fluctuating fields. The intermittent scalings of the nth-order conditional structure functions in the direction perpendicular to both the local mean field and the fluctuations agree well with the theory of Chandran, Schekochihin & Mallet, while the parallel scalings are consistent with those implied by the critical-balance conjecture. We quantify the relationship between the perpendicular scalings and those in the fluctuation and parallel directions, and find that the scaling exponent of the perpendicular anisotropy (i.e. of the aspect ratio of the Alfvénic structures in the plane perpendicular to the mean magnetic field) depends on the amplitude of the fluctuations. This is shown to be equivalent to the anticorrelation of fluctuation amplitude and alignment at each scale. The dependence of the anisotropy on amplitude is shown to be more significant for the anisotropy between the perpendicular and fluctuation-direction scales than it is between the perpendicular and parallel scales.


Age-velocity dispersion relations and heating histories in disc galaxies

Monthly Notices of the Royal Astronomical Society 462 (2016) 1697-1713

M Aumer, J Binney, R Schönrich

© 2016 The Authors.We analyse the heating of stellar discs by non-axisymmetric structures and giant molecular clouds (GMCs) in N-body simulations of growing disc galaxies. The analysis resolves long-standing discrepancies between models and data by demonstrating the importance of distinguishing between measured age-velocity dispersion relations (AVRs) and the heating histories of the stars that make up the AVR. We fit both AVRs and heating histories with formulae ∝tβ and determine the exponents βR and βz derived from in-plane and vertical AVRs and β~R and β~z from heating histories. Values of βz are in almost all simulations larger than values of β~z, whereas values of βR are similar to or mildly larger than values of β~R. Moreover, values of βz (β~z) are generally larger than values of βR (β~R). The dominant cause of these relations is the decline over the life of the disc in importance of GMCs as heating agents relative to spiral structure and the bar. We examine how age errors and biases in solar neighbourhood surveys influence the measured AVR: they tend to decrease β values by smearing out ages and thus measured dispersions. We compare AVRs and velocity ellipsoid shapes σz/σR from simulations to solar neighbourhood data. We conclude that for the expected disc mass and dark halo structure, combined GMC and spiral/bar heating can explain the AVR of the Galactic thin disc. Strong departures of the disc mass or the dark halo structure from expectation spoil fits to the data.


Determination of the shape and orientation of nonlinear magnetic structures measured by Cluster spacecraft in the vicinity of the bow shock

Journal of Geophysical Research A: Space Physics 121 (2016) 2390-2406

M Grzesiak, D Przepiórka, M Strumik, K Stasiewicz

© 2016. American Geophysical Union. All Rights Reserved.We present a new method of determination of the size and the orientation of nonlinear electromagnetic structures observed in space plasmas. The method is based on the analysis of covariance matrix of gradients of fields estimated from multipoint spacecraft measurements. It does not make use of Taylor hypothesis and gives fully three-dimensional estimates without assuming any symmetries of the structures. The method has been tested first on synthetic data and then applied to four-point Cluster spacecraft measurements to determine geometrical properties of nonlinear electromagnetic structures observed in the vicinity of the bow shock. These structures comprise ULF waves that steepen to form shocklets (short large-amplitude magnetic structures) in the foreshock region and large-amplitude mirror mode structures observed in the magnetosheath downstream of the bow shock. In the case of foreshock ULF waves we find the three-axis structure sizes of 1000, 3000, and 7000 km oriented to the ambient field at angles of 75, 30, and 60°, respectively. For the mirror modes our results give sizes of 150, 300, and 700 km oriented at angles close to the perpendicular direction for the shortest and middle scales and parallel orientation for the longest scale. The estimated geometry and properties of analyzed nonlinear structures follow, in general, those obtained previously.


Pressure-anisotropy-driven microturbulence and magnetic-field evolution in shearing, collisionless plasma

Monthly Notices of the Royal Astronomical Society 459 (2016) 2701-2720

S Melville, AA Schekochihin, MW Kunz

© 2016 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.The non-linear state of a high-beta collisionless plasma is investigated where an imposed shear amplifies or diminishes a uniform mean magnetic field, driving pressure anisotropies and, therefore, firehose or mirror instabilities. To mimic the local behaviour of a macroscopic flow, the shear is switched off or reversed after one shear time, so a new macroscale configuration is superimposed on previous microscale state. A threshold plasma beta is found: when β ≪ Ω/S (ion cyclotron frequency/shear rate), the emergence/disappearance of firehose or mirror fluctuations is quasi-instantaneous compared to the shear time (lending some credence to popular closures that assume this). This follows from the free decay of these fluctuations being constrained by the same marginal-stability conditions as their growth in the unstable regime, giving the decay time ~β/Ω ≪ S-1. In contrast, when β ≳ Ω/S, the old microscale state only disappears on the shear time-scale. In this 'ultra-high-beta' regime, driven firehose fluctuations grow secularly to order-unity amplitudes, compensating for the decrease of the mean field and thus pinning the pressure anisotropy at marginal stability without scattering particles - unlike what happens at moderate β. After the shear reverses, the shearing away of these fluctuations compensates for the increase of the mean field and thus prevents growth of the pressure anisotropy, so the system stays close to the firehose threshold, does not go mirror-unstable, the total magnetic energy barely changing at all. Implications for various astrophysical situations, especially the origin of cosmic magnetism, are discussed: collisionless effects appear mostly beneficial to fast magnetic-field generation.


Torus mapper: a code for dynamical models of galaxies

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 456 (2016) 1982-1998

J Binney, PJ McMillan


THE SEARCH FOR TRANSIENT ASTROPHYSICAL NEUTRINO EMISSION WITH ICECUBE-DEEPCORE

ASTROPHYSICAL JOURNAL 816 (2016) ARTN 75

MG Aartsen, K Abraham, M Ackermann, J Adams, JA Aguilar, M Ahlers, M Ahrens, D Altmann, T Anderson, I Ansseaus, M Archinger, C Arguelles, TC Arlen, J Auffenberg, X Bai, SW Barwick, V Baum, R Bay, JJ Beatty, JB Tjus, K-H Becker, E Beiser, S Benzvi, P Berghaus, D Berley, E Bernardini, A Bernhard, DZ Besson, G Binder, D Bindig, M Bissoki, E Blaufuss, J Blumenthal, DJ Boersma, C Bohm, M Boerner, F Bos, D Bose, S Boeser, O Botner, J Braun, L Brayeur, H-P Bretz, N Buzinsky, J Casey, M Casier, E Cheung, D Chirkin, A Christov, K Clark, L Classen, S Coenders, DF Cowen, AHC Silva, J Daughhetee, JC Davis, M Day, JPAM de Andre, C De Clercq, E del Pino Rosendo, H Dembinski, S De Ridder, P Desiati, KD de Vries, G de Wasseige, M de With, T DeYoung, JC Diaz-Velez, V di Lorenzo, JP Dumm, M Dunkman, R Eagan, B Eberhardt, T Ehrhardt, B Eichmann, S Euler, PA Evenson, O Fadiran, S Fahey, AR Fazely, A Fedynitch, J Feintzeig, J Felde, K Filimonov, C Finley, T Fischer-Wasels, S Flis, C-C Foesig, T Fucus, TK Gaisser, R Gaior, J Gallagher, L Gerhardt, K Ghorbani, D Gier, L Gladstone, M Glagla, T Gluesenkamp, A Goldschmidt, G Golup, JG Gonzalez, D Gora, D Grant, JC Groii, A Gross, C Ha, C Haack, AH Ismail, A Hallgren, F Halzen, E Hansen, B Hansmann, K Hanson, D Hebecker, D Heereman, K Helbing, R Hellauer, S Hickford, J Hignigiit, GC Hill, KD Hoffman, R Hoffmann, K Holzapfel, A Homeier, K Hoshina, F Huang, M Huber, W Huelsnitz, PO Hulth, K Hultqvist, S In, A Ishihara, E Jacobi, GS Japaridze, K Jero, M Jurkovic, A Kappes, T Karg, A Karle, M Kauer, A Keivani, JL Kelley, J Kemp, A Kheirandish, J Kiryluk, J Klaes, SR Klein, G Kohnen, R Koirala, H Kolanoski, R Konietz, L Koepke, C Kopper, S Kopper, DJ Koskinen, M Kowalski, K Krings, G Kroll, M Kroll, J Kunnen, N Kurahashi, T Kuwabara, M Labare, JL Lanfranchi, MJ Larson, M Lesiak-Bzdak, M Leuermann, J Leuner, L Lu, J Lunemann, J Madsen, G Maggi, KBM Mahn, R Maruyama, K Mase, HS Matis, R Maunu, F McNally, K Meagher, M Medici, A Meli, T Menne, G Merino, T Meuress, S Miarecki, E Middell, E Middlemas, L Mohrmann, T Montaruli, R Morse, R Nahnhauer, U Naumann, G Neer, H Niederhausen, SC Nowicki, DR Nygren, A Obertacke, A Olivas, A Omairat, A O'Murchadha, T Palczewski, H Pandya, DV Pankova, L Paul, JA Pepper, C Perez de los Heros, C Pfendner, D Pieloth, E Pinat, J Posselt, PB Price, GT Przybylski, J Puetz, M Quinnan, C Raab, L Raedel, M Rameez, K Rawlins, R Reimann, M Relich, E Resconi, W Rhode, M Richman, S Richter, B Riedel, S Robertson, M Rongen, C Rott, T Ruhe, D Ryckbosch, SM Saba, L Sabbatini, H-G Sander, A Sandrock, J Sandroos, S Sarkar, K Schatto, F Scheriau, M Schimp, T Schmidt, M Schmitz, S Schoenen, S Schoeneberg, A Schoenwald, L Schulte, D Seckel, S Seunarine, MWE Smith, D Soldin, M Song, GM Spiczak, C Spiering, M Stahlberg, M Stamatikos, T Stanev, NA Stanisha, A Stasik, T Stezelberger, RG Stokstad, A Stoessl, R Strom, NL Strotjohann, GW Sullivan, M Sutherland, H Taavola, I Taboada, J Tatar, S Ter-Antonyan, A Terliuk, G Tesic, S Tilav, PA Toale, MN Tobin, S Toscano, D Tosi, M Tselengidou, A Turcati, E Unger, M Usner, S Vallecorsa, J Vandenbroucke, N van Eundhoven, S Vanheule, J van Santen, J Veenkamp, M Vehring, M Voge, M Vraeghe, C Walck, A Wallace, M Wallraff, N Wandkowsky, C Weaver, C Wendt, S Westerhoff, BJ Whelan, N Whitehorn, K Wiebe, CH Wiebusch, L Wille, DR Williams, H Wissing, M Wolf, TR Wood, K Woschnagg, DL Xu, XW Xu, Y Xu, JP Yanez, G Yodh, S Yoshida, M Zoll


AWAKE: A Proton-Driven Plasma Wakefield Acceleration Experiment at CERN

Nuclear and Particle Physics Proceedings 273-275 (2016) 175-180

C Bracco, LD Amorim, R Assmann, F Batsch, R Bingham, G Burt, B Buttenschön, A Butterworth, A Caldwell, S Chattopadhyay, S Cipiccia, LC Deacon, S Doebert, U Dorda, E Feldbaumer, RA Fonseca, V Fedossev, B Goddard, J Grebenyuk, O Grulke, E Gschwendtner, J Hansen, C Hessler, W Hofle, J Holloway, D Jaroszynski, M Jenkins, L Jensen, S Jolly, R Jones, MF Kasim, N Lopes, K Lotov, SR Mandry, M Martyanov, M Meddahi, O Mete, V Minakov, J Moody, P Muggli, Z Najmudin, PA Norreys, E Öz, A Pardons, A Petrenko, A Pukhov, K Rieger, O Reimann, AA Seryi, E Shaposhnikova, P Sherwood, LO Silva, A Sosedkin, R Tarkeshian, RMGM Trines, FM Velotti, J Vieira, H Vincke, C Welsch, M Wing, G Xia

© 2015 Elsevier B.V..The AWAKE Collaboration has been formed in order to demonstrate proton-driven plasma wakefield acceleration for the first time. This acceleration technique could lead to future colliders of high energy but of a much reduced length when compared to proposed linear accelerators. The CERN SPS proton beam in the CNGS facility will be injected into a 10 m plasma cell where the long proton bunches will be modulated into significantly shorter micro-bunches. These micro-bunches will then initiate a strong wakefield in the plasma with peak fields above 1 GV/m that will be harnessed to accelerate a bunch of electrons from about 20 MeV to the GeV scale within a few meters. The experimental program is based on detailed numerical simulations of beam and plasma interactions. The main accelerator components, the experimental area and infrastructure required as well as the plasma cell and the diagnostic equipment are discussed in detail. First protons to the experiment are expected at the end of 2016 and this will be followed by an initial three-four years experimental program. The experiment will inform future larger-scale tests of proton-driven plasma wakefield acceleration and applications to high energy colliders.


Characteristics of betatron radiation from direct-laser-accelerated electrons

Physical Review E - Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics (2016)

PA Norreys


Very high-energy gamma-ray follow-up program using neutrino triggers from IceCube

Journal of Instrumentation 11 (2016)

MG Aartsen, K Abraham, M Ackermann, J Adams, JA Aguilar, M Ahlers, M Ahrens, D Altmann, K Andeen, T Anderson, I Ansseau, G Anton, M Archinger, C Argüelles, J Auffenberg, S Axani, X Bai, SW Barwick, V Baum, R Bay, JJ Beatty, J Becker Tjus, KH Becker, S BenZvi, D Berley, E Bernardini, A Bernhard, DZ Besson, G Binder, D Bindig, M Bissok, E Blaufuss, S Blot, C Bohm, M Börner, F Bos, D Bose, S Böser, O Botner, J Braun, L Brayeur, HP Bretz, S Bron, A Burgman, T Carver, M Casier, E Cheung, D Chirkin, A Christov, K Clark, L Classen, S Coenders, GH Collin, JM Conrad, DF Cowen, R Cross, M Day, JPAM De André, C De Clercq, E Del Pino Rosendo, H Dembinski, S De Ridder, P Desiati, KD De Vries, G De Wasseige, M De With, T DeYoung, JC Díaz-Vélez, V Di Lorenzo, H Dujmovic, JP Dumm, M Dunkman, B Eberhardt, T Ehrhardt, B Eichmann, P Eller, S Euler, PA Evenson, S Fahey, AR Fazely, J Feintzeig, J Felde, K Filimonov, C Finley, S Flis, CC Fösig, A Franckowiak, R Franke, E Friedman, T Fuchs, TK Gaisser, J Gallagher, L Gerhardt, K Ghorbani, W Giang, L Gladstone

© 2016 IOP Publishing Ltd and Sissa Medialab srl.We describe and report the status of a neutrino-triggered program in IceCube that generates real-time alerts for gamma-ray follow-up observations by atmospheric-Cherenkov telescopes (MAGIC and VERITAS). While IceCube is capable of monitoring the whole sky continuously, high-energy gamma-ray telescopes have restricted fields of view and in general are unlikely to be observing a potential neutrino-flaring source at the time such neutrinos are recorded. The use of neutrino-triggered alerts thus aims at increasing the availability of simultaneous multi-messenger data during potential neutrino flaring activity, which can increase the discovery potential and constrain the phenomenological interpretation of the high-energy emission of selected source classes (e.g. blazars). The requirements of a fast and stable online analysis of potential neutrino signals and its operation are presented, along with first results of the program operating between 14 March 2012 and 31 December 2015.


Theory of Thomson scattering in inhomogeneous media.

Scientific reports 6 (2016) 24283-

PM Kozlowski, BJ Crowley, DO Gericke, SP Regan, G Gregori

Thomson scattering of laser light is one of the most fundamental diagnostics of plasma density, temperature and magnetic fields. It relies on the assumption that the properties in the probed volume are homogeneous and constant during the probing time. On the other hand, laboratory plasmas are seldom uniform and homogeneous on the temporal and spatial dimensions over which data is collected. This is particularly true for laser-produced high-energy-density matter, which often exhibits steep gradients in temperature, density and pressure, on a scale determined by the laser focus. Here, we discuss the modification of the cross section for Thomson scattering in fully-ionized media exhibiting steep spatial inhomogeneities and/or fast temporal fluctuations. We show that the predicted Thomson scattering spectra are greatly altered compared to the uniform case, and may lead to violations of detailed balance. Therefore, careful interpretation of the spectra is necessary for spatially or temporally inhomogeneous systems.


Radio Galaxy Zoo: Discovery of a poor cluster through a giant wide-angle tail radio galaxy

Monthly Notices of the Royal Astronomical Society 460 (2016) 2376-2384

JK Banfield, H Andernach, AD Kapińska, L Rudnick, MJ Hardcastle, G Cotter, S Vaughan, TW Jones, I Heywood, JD Wing, OI Wong, T Matorny, IA Terentev, R López-Sánchez, RP Norris, N Seymour, SS Shabala, KW Willett

© 2016 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.We have discovered a previously unreported poor cluster of galaxies (RGZ-CL J0823.2+0333) through an unusual giant wide-angle tail radio galaxy found in the Radio Galaxy Zoo project. We obtained a spectroscopic redshift of z = 0.0897 for the E0-type host galaxy, 2MASX J08231289+0333016, leading to Mr = -22.6 and a 1.4 GHz radio luminosity density of L1.4 = 5.5 × 1024 W Hz-1. These radio and optical luminosities are typical for wide-angle tailed radio galaxies near the borderline between Fanaroff-Riley classes I and II. The projected largest angular size of ≈8 arcmin corresponds to 800 kpc and the full length of the source along the curved jets/trails is 1.1 Mpc in projection. X-ray data from the XMM-Newton archive yield an upper limit on the X-ray luminosity of the thermal emission surrounding RGZ J082312.9+033301 at 1.2-2.6 × 1043 erg s-1 for assumed intracluster medium temperatures of 1.0-5.0 keV. Our analysis of the environment surrounding RGZ J082312.9+033301 indicates that RGZ J082312.9+033301 lies within a poor cluster. The observed radio morphology suggests that (a) the host galaxy is moving at a significant velocity with respect to an ambient medium like that of at least a poor cluster, and that (b) the source may have had two ignition events of the active galactic nucleus with 107 yr in between. This reinforces the idea that an association between RGZ J082312.9+033301 and the newly discovered poor cluster exists.


Evidence that the maximum electron energy in hotspots of FR II galaxies is not determined by synchrotron cooling

Monthly Notices of the Royal Astronomical Society 460 (2016) 3554-3562

AT Araudo, AR Bell, A Crilly, KM Blundell

© 2016 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.It has been suggested that relativistic shocks in extragalactic sources may accelerate the highest energy cosmic rays. The maximum energy to which cosmic rays can be accelerated depends on the structure of magnetic turbulence near the shock but recent theoretical advances indicate that relativistic shocks are probably unable to accelerate particles to energies much larger than a PeV. We study the hotspots of powerful radiogalaxies, where electrons accelerated at the termination shock emit synchrotron radiation. The turnover of the synchrotron spectrum is typically observed between infrared and optical frequencies, indicating that the maximum energy of non-thermal electrons accelerated at the shock is ≲ TeV for a canonical magnetic field of ~100 μG. Based on theoretical considerations we show that this maximum energy cannot be constrained by synchrotron losses as usually assumed, unless the jet density is unreasonably large and most of the jet upstream energy goes to non-thermal particles. We test this result by considering a sample of hotspots observed with high spatial resolution at radio, infrared and optical wavelengths.


Rejuvenation of stellar mergers and the origin of magnetic fields in massive stars

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 457 (2016) 2355-2365

FRN Schneider, P Podsiadlowski, N Langer, N Castro, L Fossati


Effect of the Shafranov shift and the gradient of β on intrinsic momentum transport in up-down asymmetric tokamaks

Plasma Physics and Controlled Fusion 58 (2016)

J Ball, FI Parra, J Lee, AJ Cerfon

© 2016 IOP Publishing Ltd Printed in the UK.Tokamaks with up-down asymmetric poloidal cross-sections spontaneously rotate due to turbulent transport of momentum. In this work, we investigate the effect of the Shafranov shift on this intrinsic rotation, primarily by analyzing tokamaks with tilted elliptical flux surfaces. By expanding the Grad-Shafranov equation in the large aspect ratio limit we calculate the magnitude and direction of the Shafranov shift in tilted elliptical tokamaks. The results show that, while the Shafranov shift becomes updown asymmetric and depends strongly on the tilt angle of the flux surfaces, it is insensitive to the shape of the current and pressure profiles (when the geometry, total plasma current, and average pressure gradient are kept fixed). Next, local nonlinear gyrokinetic simulations of these MHD equilibria are performed with GS2, which reveal that the Shafranov shift can significantly enhance the momentum transport. However, to be consistent, the effect of β′ (i.e. the radial gradient of β) on the magnetic equilibrium was also included, which was found to significantly reduce momentum transport. Including these two competing effects broadens the rotation profile, but leaves the on-axis value of the rotation roughly unchanged. Consequently, the shape of the β profile has a significant effect on the rotation profile of an up-down asymmetric tokamak.

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